Expansible underreamer



March 17, 1931. a. H. SCOTT ET AL 1,796,543

EXPANS IBLE UNDERREAMER Filed Ap-ril 12 93 3 Sheets-Sheet l 1 .z. v a

lli'l l Zjim j'oad EPA/APB 666777 4MVL 5 F066 AJE/l. J 92/6,

3 Sheets-Sheet 3 B. HJSCOTT ET AL EXPANSIBLE UNDERREAMER Filed April 12 1925 m. m 4/, ma 0 0 Z5? n 5/ w 4 I M MM gwm & 5 4 w m5 HIM IH l HIM H March 17, 1931.

Patented Mar. 17, 1931 UNITED STATES PATENT OFFICE BERNARD H. SCOTT, OF GLENDALE, SAMUEL E. ROSS, 0! LONG BEACH, AND NEIL J. NORRIS, OF SANTA FE SPRINGS, CALIFORNIA, ASSIGNORS, BY MESIQ E ASSIGNMENTS, 'I'O JOHN GRANT, 01 LOS ANGELES, CALIFORNIA EXPANSIBLE UNDEBREAMER Application filed April 12,

Our invention relates to expansible under reamers such as are used in deep well operations; and more particularly to expansible rotary underreamers.

In the oil producing industry, a string of casing is placed in a well, when cores taken from the well indicate that the oil bearing sand has been encountered. It is sometimes found that after this string of easing has been installed and tightly cemented above the oil bearing horizon that it is necessary to drill the well to a lower depth for commercial production.

It is impossible to withdraw the cemented casing and impractical to drill a smaller hole below same, as it is good practice to retain as large a diameter as possible in the well casing to simplify deeper drilling, should it prove necessary to drill to additional depth.

It is also very desirable to have as large an annular area between a string of well casing and the wall of the hole as possible, in order to place a sufiicient amount of cement outside of the casing, should it prove necessary to shut off a second water sand in the well.

When such circumstances arise, or where, for any reason it is desired to deepen the hole below set casing and subsequently set another string of casing,.it is the custom to deepen the well with a bit which will readily pass through the cemented casing, and then to underream this new part of the well to a size which will receive the second string of easing freely, and allow sufficient annular space between said second string of casing and the wall of the hole to properly cement same, should it become necessary to do so.

By this method, the real oil bearing sands may be reached and the second string of casing lowered into the underreamed hole to whatever depth is desired.

For this purpose various underreamers have been devised, the ein most instances be ing secured in the drill string just above the pit.

It is a broad object of our lnventlon to provide an expansible underreamer in which cutting elements are automatically expanded 1926. Serial No. 101,456.

into underreaming or expanded position when the underreamer asses downwardly out of the lower mouth of the casing.

A very common difficulty experienced with many expansible underreamers now in use is in the unequal expansion of the different cutting elements thereof. This results in what is known as bulldogging, which causes the underreamer to bind while it is being lowered through the oil string, requiring it to he withdrawn and re-set, or a tendency by the underreamer to deflect the bit from the true axis in which it is drilling.

It is an object of our invention to provide an expansible roller underreamer in which the cutting elements thereof are expanded simultaneously and automatically a uniform distance from the axis of the underreamer when the latter passes downwardly out of the casing.

Another object is to rovide a rotary expansive underreamer of simple, rugged and durable structure and design; and one in which the cutter elements are strongly and rigidly supported in their expanded positions, both as regards inward and upward stresses and as regards tangential stresses which have a tendency to tear the cutters from the body.

Other objects and advantages will be made manifest in the following description and accompanying drawings, in which:

Fig. 1 is a diagrammatic view showing the oil well in section and illustrating the use to which our improved underreamer is put;

Fig. 2 is an elevational view of our improved underreamer partially broken away to illustrate certain details of its construction.

Fig. 3 is a vertical sectional view through a cutter holding member taken on the line 3-3 of Fig. 2.

Fig. 4 is a view of our underreamer just before leaving or just after entering the lower end of a section of well casing, one of the body forming sections being removed to slhow the position of the parts normally hid- Fig. 5 is a view similar to Fig. 4 in which the underreamer has sufficiently emerged from the end of a section of well casing so is bein drawn.

Figs. Z, 6 and i? are horizontal sectional views telren upon the lines '?7, 8--6 and 9-4) respectively of Fig. 5, and showing details of construction of our underreamer.

Fig. 10 is a View in perspective of one of the sections which are secured together to form the body of our undcrreamer.

Referring specifically to the drawings, Fig. 1 shows an oil well in which an outer oil well casing 16 has been sunk to the point 1.7 where the bottom end of the casing 16 has been cemented in place, as shown. Below the point 17 the oil well 15 has been deepened with a diameter equal to the inside diameter substantially of the casing 16 to the point 19 and a new strin of casing'18 has been sunk in the deepened portion of the well to the point 19 and has been cemented ofi there, as shown. The well has thereafter been deepened with a diameter substantially equal to that of the inside of the casing 18 to the point 26 and an inner casing 21 or what is usually called an oil string has been installed in the well which reaches down to the point 20.

For reasons which have been mentioned heretofore, after stopping the drilling of the well at the point 20 and the sinking of the casing 21 in the well to this point, it is necessary to deepen the well 15 below the point 20 and sink the casing 21 farther downwardly in the well. For this purpose a fish-tail bit 25 secured upon the lowermost end of a string of drill pipe 26 is inserted downwardly through the innermost string of well casing 21. The drill pipe 26 extends upwardly above the upper end 27 of the well casing 21 through a rotary table 28 and is suspended by a rotary swivel head 29 which is attached through a removable link 30 to a traveling block 31 of the hoisting rigging of a derrick (not shown), which is disposed directly above the well 15. Attached to the swivel head 29 is a rotary fiuid hose 34 which connects to a stand pipe 35 extending upwardly a given distance, from a high pressure slush pump 36 which is operated by steam passing through a steam line 37 which leads to a suitable boiler (not shown). A slush pump inlet pipe 38 has a lower end 35 disposed beneath the surface of the liquid in a. rotary fluid sump and extends upwardly as shown, connecting to the inlet of the slush pump 36. The rotary table 28 is diagrammatically shown and is of the usual type which is adap ed to be rotated for the purpose of rotating the string of drill pipe 26.

Cennected in the string of ween the lowermost sectioi' 5 is the underreamer d6 of our invention. "his underreamer has a body (i7 formed of sections tive in Fig. 10. In the construction of the prcsentembodiment the sections 48 are two in number, having a semicylindrical fore, and are provided with holes 4-9 and at the ends of which are formed recesses 51, the holes 49 and 50 and recesses 51 being adapted to receive bolts having nuts 53 which secure the halves 48 together to form the cylindrical body d7 of the underreamcr. The body 47 has a pin member 54 at its upper end and a pin member 55 at its lower end, the pin members 54 and 55 being adapted to threadedly engage with tool joint members 57 and 58 for securing the underreamer to adjacent ends of the string of drill pipe 26.

Each of the half sections 48 has a parting surface 60 which meets the parting surface 60 of the opposing identical member 48 when the two are ]OlI1d. together to form the body 47. Machined out from the surface 60 adjacent to the opposite edges thereof are symmetrical recesses 61. These recesses extend inwardly almost to the axis of the section 46 so that a web of metal remains unremoved. The inner portion of the surface 66 of the recesses 61 is cut away to form a deepened channel 67 which extends the full length of the recess 61, and has at its outer edge an inwardly facing shoulder 68. lhe deepened channels 67 are therefore bounded on the outside by the shoulders 68 and on the inside by the web 65 as clearly shown in Fig. 10. When the body halves are assembled, the recesses 61 with their undercut channels 67 then form opposed longitudinally extending cutter receiving slots which have undercut side walls, the slot bottoms being formed by the web 65. This will be readily understood from the cross-sectional views.

Bounding the upper end of each recess 61 and its deepened channel 67 and formed in the upper head portion of each half body section 48 is an irregular surface 76. This irregular surface begins at the upper end of the web 65, projects upwardly and outwardly at an obtuse angle to the vertical to form a traversing cam face 77, then projects upwardly and outwardly at an acute angle to the vertical to form a forcing c m face 78, then projects upwardly and outwardly at substantially the same angle as the face 77 to form an abutting face 79, then projects downwardly and outwardly, as shown, to form an inwardly facing retaining face or shoulder 80. The purpose of the surface 76 formed as just described will be made apparent in the later description. Vheu the body parts are assembled, the spaces enclosed by the several described faces, which faces in the body halves register with each other,

one of which. is shown. in perspeclit avsassa 88 of a septum 90. The septum 90, which is in effect a downward continuation of web 65 below boss 85, projects downwardly a given distance from the boss 85 for a purpose to be described later.

Bounding the lower end of each recess 61 and channel 67 is a face 95 provided upon opposite sides of the foot portion 96 of each of the half body sections 48. These faces 95 incline inwardly and downwardly at a slight angle from the horizontal. Formed in the parting surface 60 of the foot portion 96 is a semi-cylindrical recess 98 which communicates between the recesses 61 and the lower end of the half 100 of the pin member 55 which is formed on the foot 96 of each half body section 48. Internal threads 101 are formed within the lower portion of the recess 98.

Channeled from the surface 60 of the upper head portion 75 of each half body section 48 are two semi-cylindrical grooves 105 which have lower portions 106 of reduced diameter,

the grooves 105 extending between the upper end 107, of the half 108 of the pin 54 which is formed upon the head 75, and the face 77 of the surface 7 6; A bolt hole 49 is formed in the head between the channels 106 as shown.

The two half body sections 48 are securely joined together as shown in Fig. 2 by the bolts 52 and the nuts 53 which pass through the holes 49 and 50, as previously described. When so assembled, the various channels, recesses and surfaces of the body halves register as will be well understood from a consideration of the drawings. When the half body sections 48 are thus united in register, the recesses 61 of the opposing half body sections 48 unite to form cutter carrier retaining pockets or slots 110. Cutter carriers 112 aredisposed in the pockets 110 during the assembling of the body halves 48. The cutter carriers112 have side faces 113 which slidingly engage the side surfaces 66 of the recesses 61. At the rear edge of the faces 113 laterally projecting vertical ribs 114 are formed upon the cutter carriers 112. The ribs 114'as clearly shown in Fig. 8 are of less depth than the width of the decpcned channels 67. It will therefore be sccn that the cutter carriers 112 have freedom to slide I I between a retracted position, in which the shown in retracted position, while in F ig. i

the cutter carriers 112 are shown in extended position.

The portion of the parting surface 30, which is not cut away i the forming of the body half sections 48.. extends from the head 75 along the top of the web 65, the boss and the septum 90. As all portions of the two facesGO are in close contact when the body half sections 48 are assembled, the webs 65 form a continuous wall 116 extending longitudinally between the head portions 75 and the foot portions 96 in the assembled underreamer and lying between the cutter receiving slots 110. This wall 116 is enlarged at the bosses 35 and occupies a central space of such size as requires the cutter carriers 112 to be cut away at 117, asclearly shown in Figs. 4 and 5, inorder that the cutter carriers 112 may be shifted inwardly to retracted position. This cutting away of the cutter carriers 112 provides cam faces 118 which engage with the faces 87 when. the cutter carriers 112 are in retracted position as shown in 4.

When the cutter carriers 112 are in expandedposition in the cavities as shown in Fig. 5, the inner faces 120 of the lower projecting portions 121 of the cutter carriers 112 are in contact with the outer surfaces 86 of the boss 85. The expansion of the cutter carriers 112 forms open spaces 124 between the inner faces 125 of the carriers 112 and the central wall 116. The upper ends of these spaces 124 are bounded by the traversing faces 7 7 and communicate with the lower restricted portions 106 of the fluid channels 105. Communicating between the lower ends of the spaces 124 and the space below the lower faces 128 of the cutter carriers 112, are grooves 129 formed in the faces 120 of the lower ends 121 of the cutter carriers 112, these grooves allowing passage of fluid from spaces 124 past the cutter carriers so circulation through the underreamer may be had when it is in expanded condition as will hereinafter appear.

Each of the cutter carriers 112has recesses 130 and 131- formed inwardly from the outside edges thereof to a vertical plane 132; Milled inwardly from the plane 132 in each of the recesses 130. and 131 are cylindrical cavities 133 and134 respectively. -The cavity 134 has a frusto-conical cavity 135 formed from the lower end thereof. The lower portion of the cutter carriers 112 has an outer surface 138 which when the carriers are in extended position is of the same radius or slightly larger radius than that of the underreamer body 48. A wall 139 remains integral with the body of the carriers 112 between the cavities 133 and 134 as clearly shown in Figs. 3, 4 and 5. The wall 139 has an outer cylindrical surface 140 which is of a slightly larger radius, when the carriers are in extended position, than the surfaces 138 of the lower portions 121. The upper portions 142 of the carriers 112 have outer surfaces 143 which are larger in radius than that of surfaces 140 but of slightly less radius than that of thehole of the well after it has been enlarged by the underreamer 46. As shown in Fig. 3 the upper portion 142 of the cutter carriers 112 is formed so as to fit into the recess enclosed by the irregular surfaces 76 formed in the head portion 75 of the body.

Thus when the carriers are in extended position, the upper end of each has a surface 145 which contacts with the face 80, a surface 146 which contacts with the abutting face 79, and aforcing cam surface 147 which contacts the cam face 78.

Disposed in the cavity 133 is a roller reaming cutter 150 which has upper andlower cutting portions 151 and 152 provided with peripheral cutting faces. Disposed 1n the cavit 134 is a cylindrical roller cutter 153 whic has a. peripheral cutting face and a frusto-conical lower portion 154 provided with a cutting face. Rollers 150 and 153 have central cylindrical cavities 155 and 156. A pin receiving hole 158 is bored as shown in Fig. 3 through the lower portion 121, the wall portion 139 and into the upper portion 142 of each cutter carrier 112. A roller carrying pin 160 is introduced upwardly into the hole 158 and passes through holes 156 and 155 in the cutters 153 and 150 so as to retain the cutters for rotation in their respective cavities. The pin 160 is held securely in place in the hole 158 by a screw 161 which .is screwed through an opening 162 formed in the lower carrier ortion 121, and into a threaded hole 163 which is formed in the cutter in 160.

T e cutter assemblies which have just been described each comprises specifically a cutter carrier and a cutter or cutters proper. As described, they are of the form we prefer. However, the nature of the cutters proper (the ultimate cuttting edges etc.,), depending as it does on the character of formation being reamed, may be varied widely, and consequently the make-up of the cutter assembly may vary widely. In the ensuing claims we have therefore used the term cutter element as an inclusive one to denote an element which has the characteristics of the part which we have here specifically called the cutter carrier but which may carry the actual'cutting edge or ed es in any desired manner.

A follower 164 in the form of a cylindrical shell is disposed in the cylindrical cavity 165 formed by the uxtaposition of the semicylindrical cavities 98 formed in the foot portions 186 of the body half sections 48. The

means follower 164 is provided with longitudinal slots 166 which open from the upper end 167 thereof downwardly to within a given distance of the lower end 168 of the follower 165. The upper end 167 of the follower 164 is always in contact with the lower surfaces 128 of the cutter carriers 112. The follower 164 is retained against rotation by the sliding of the slots 166 over the septums 90.

Notches 169 are formed laterally in the upper end 167 of the follower 164 for a purpose to be described later. Also disposed in the cylindrical cavity 165 beneath the follower 164 is a compression spring 170, the upper end of which bears against the lower end 168 of the follower 164 and the lower end of which rests upon a threaded bushing 171 which has a central openin 172 therein and which is screwed into the t ireads 101 in the lower end of the opening 165. The spring 170 exerts a contant u ward pressure which 18 transmitted throug the follower 164 to the cutter carriers 112 and which tends to constantly retain the cutter carriers in their upward position in which they are shown in Fig. 5.

The hole bored by the bit 25 is of but slightly larger diameter than the diameter of the body 47 of the underreamer 46. This d ameter being slightly less than the inside diameter of the casing 21, the bit 25 and the underreamer body 47 may be easily assed downwardly through the casing 21. ln order that the cutter carriers 112 may not extend outwardly beyond the radius of the inside surface 185 of the casing 21, they are forced into retracted position as shown in Fig. 4 before the underreamer enters the upper end of the casing 21. In this position of the cutter carriers 112 outer corners 186 of the upper portions 142 of the carriers 112 contact with the inner surface 185 of the easing 21. This is due to the surface 143 of the upper portions 142 of the cutter carriers 112 being curved in an arc of substantially the radius to which the underreamer is adapted to ream the hole dug by the bit 25, which hole is larger than the outside diameter of the casing 21. The cutter carriers 112 are therefore retained, by this engagement of the points 186 with the surface 185, in a retracted position in which the teeth of the cutter members 150 and 153 will be retained inwardly out of contact with the inside wall 185 of the casing 21, see Fig. 6. This obviously protects the teeth 187, which are formed vertically upon the periphery of the cutters 150 and 153, from being worn by such frictional contact. This feature of our invention overcomes a weakness of many underreamers in which the retaining of the cutting-members in retracted position during the passage of the underreamer downwardly through the casing is effected by contact of the casing.

Although in Fig. 6 the teeth 187 of the cutters 150 and 153 are shown as coming very close to the surface 185 of the casing 21, it is possible for the outer arcuate surface 143 of the portion 142 of the cutter carriers 112 to be broadened so that the cutters 150 and 153 are retained a considerable distance from contact with the surface 185 of the casing 21 by the contact of corners 186' withthe surface 185.

As the underreamer emerges from the lowor end of the casing 21 as shown in Fig. 4, the corners 186 move downwardly out of engagement with the inner surface 185 of. the casing 21, and the cutter carriers 112 become free to move outwardly with respect to-the body 47 of the underreamer 46. The upward pressure of the spring 170 being constantly applied to the lower end of the cutter carriers 112 through the follower 164, contact between the cutter carrier surfaces 118 and the underreamer body surfaces 87 as well as the contact between the cutter carrier surfaces 146 and the underreamer bodysurface 77 tends to move the cutter carriers 112 outwardly with respect to the body 47 of the underreamer. Inasmuch as the underreamer body surfaces 77 and 87 are substantially parallel, the outward movement of the cutter carriers 112, as the corners 186 become released from engagement with the inner surface 185 of the casing 21, will be a movement of translation as long as the cutter carrier surfaces 146 and 118 both remain in contact respectively with the underreamer body surfaces 77 and 87. As clearly shown in Fig 4, however, the inner ed'ges 190 of the cutter carrier surfaces 146 will ride off the body surfaces 77, while the cutter carrier surfaces 118 are still in contact with the underreamer body surfaces 87. After the edge 190 has passed over the outer edge 194 of the underreamer body surface 77, the outward movement of the upper end 142 of each cutter carrier 112 will be determined by the contact between the cutter carrier surface 147 and the underreamer body surface 78. It is obvious, however, that the outward movement of the upper ends of the cutter carriers caused by the contact of the cutter carrier surfaces 147 with the underreamer body surfaces 78 will be at a much slower rate than the outward movement of the lower end of the cutter carriers, due. to the continued contact of the cutter carrier cam surfaces 118 with the underreamer bit cam surfaces 87.

The outward movement of the cutter car riers 112, due to its being forced upwardly by the spring 170, may thus be resolved into three stages. In the first stage, the upper and lower ends of the cutter carriers are moved upwardly and outwardly in parallelism. This sta e ends when the ed 190 crosses outwar ly the edge 194. In t e second stage, which then begins, the lower ends of the cutter carriers continue to move outwardly at the same rate at which they started, while the upper ends of the cutter carriers move outwardly at a decreased rate due to the decreased inclination of the cooperating cam surfaces upon the. upper ends of the cutter carriers and the underreahner body which are then in engagement. During the second stage of movement the lower ends of the cutter carriers are moved outwardly a considerably greater distance than the upper ends of the cutter carriers. The end of the second stage is reached when the inner edge of the cutter carrier surfaces 118 rides outwardly over the outer edge of the underreamer body surfaces 87. At this time the lower portions of the cutter carriers are disposed at their outermost position, while the upper ends of the cutter carriers have yet a considerable distance to move in order to reach their outermost position. During the third stage of the outward movement of the cutter carriers, the lower portions thereof, due to the sliding engagement of the carrier surfaces 120 and the parallel underreamer body surfaces 86, move upwardly in parallel paths, while the upper portions continue outwardl to their completely extended positions. he cutter carriers are shown at the completion of the iil rird stage of their outward movement in It is not possible to lift the casin 21 as the underreamer 46 emerges from 18%01313011'1 of the casing. It is therefore a feature of great value in our underreamer that the lower cutters 153 are extended outwardl in advance of the upper cutters 150. T is protrusion outwardly of the cutters 153 in advance of the upper part of the cutter carriers 112 enlarges the hole dug by the bit 25 so that as the underreamer is fed downwardly completely out of the lower mouth of the casing 21, space is rovided in which the upper portions 142 of the cutter carriers 112 may expand into extended position.

When the deeper portion 180 of the well 15 has been reamed downwardly to the desired depth, the drill strin 26 is drawn upwardly out of the hole. en the underreamer enters the mouth of the casing-21, as shown in Fig. 5, upper cam beveled surfaces 200 formed upon the upper portion 142 of the cutter carriers 112, between the surfaces 143 and the surfaces 145, engage the mouth of the casing 21 as shown. When the underreamer body 47 is drawn further up- Wardly by the drill string 26 the engagement of the surfaces 200 with the lower end of the casing 21 causes the cutter carriers 112 to be retained against upward movement, while the body 47 continues to ascend, and the beveled angle of the surfaces 200 causes the cutter carriers 112 to move inwardly as they are so retained. As the body 47 ascends, the irregular surfaces 76 formed on head portion 7 are withdrawn from upper carrier portions 142, and the boss 85 is withdrawn from between the inner faces 120 of the cutter carriers, thus permitting the cutter carriers to be forced inwardly by sliding of the surfaces 200 against the lower end of the casing 21. This results eventually in the movement of the cutter carriers 112 from extended position shown in Fig. 5 to completely retracted position shown in Fig. 4. Immediately upon reaching the retracted position, the cutter carriers slide upwardly inside the casing 21, only the corners 186 of the upper ends 142 of the cutter carriers 112 contacting the inside surface of the casing 21 during theraisin of the underreamer out of the well.

It will be seen that when the cutters are in the retracted position of Figure 4, the upper ends of grooves 129 are closed by the lower faces 87 of la 85, thus preventing the passage of fluid rom assages 105 to bore 165 at the bottom of t e underreamer. However when the cutters are moved to the exanded position of Figure 5, fluid may pass rom passageways 105 through recesses 124, grooves 129 since the latter are then uncovered by virtue of the lateral displacement of the cutter carriers) and the bore of follower sleeve 164 to bore 165 and thence throu h sleeve nut 171 to bit 25 where it is delivered through usual outlets 25a to the well bore for usual lubricating and flushing purposes. Thus, assuming that pressure be kept on the fluid within the drill stem as the latter is lowered, the fact that the fluid pressure pumps labor or are stopped entirely, indicates that the reamer has not become expanded, while the instant circulation is restored due to the uncovering of passages 129 by lateral movement of the cutter carriers and as evidenced by the picking-up of the pumps, the operator knows that the reamer cutters are in expanded ositions. The advantage of this indicating feature is self evident. v

When the cutters are expanded a portion of the circulating fluid is diverted from the bore of sleeve follower 164 through notches 169 in said follower, this diverted fluid being delivered substantiall immediately beneath the cutter carriers an serving as a lubricant and flushing medium for the cutters.

It will be understood that we do not conceive of our invention being limited in all those details we have particularly described. Our detailed enumeration and description of the complete underreamer is with the view of acquainting those skilled in this art with one specific and preferred embodimentof the invention, and not with the view of limiting the invention thereto except as is expressly so stated in the following claims. Those familiar with the art will recognize many modifications and changes which may be made without departing from the inventions essence, and therefore which we need not attempt here to enumerate.

We claim as our invention: 1. In an underreamer, the combination of: a body member; cutting elements; means for shiftably mounting said cutting elements upon said body member so that each has extended and retracted positions relative to said bod member; means for yieldingly urging sai cutting elements from retracted position to extended position, said last mentioned means causing the lower portions of said cutting elements to approach extended position at a faster rate than the upper portions thereof during the intermediate portion of the movement of the cutting elements; and means contacting the inner surface of a well casing, through which said underreamer is passed, to retain said cutting elements in retracted position.

2. In an underreamer, the combination of: a body member; cutting elements; means for shiftably mounting said cutting elements upon said body member so that each has extended and retractedpositions relative to said body member; means for yieldingly urging said cutting elements from retracted position to extended position, said last mentioned means causing the lower portions of said cutting elements to reach extended position sooner than the upper portions thereof.

3. In an underreamer, the combination of: a body member; cutting elements provided with peripheral cuttin faces; means for shiftably mounting said cutting elements upon said body member so that each has extendedand retracted positions relative to said bod member; means for yieldingly urging sai cutting elements from retracted position to extended position; means contacting the inner surface of a well casin through which said underreamer is passe to retain said cutting elements in retracted position; and means for causing said cutting elements to move from extended position to retracted position out of frictional contact with the casing when said underreamer is drawn upwardly into said casing.

4. In an underreamer, the combination of: a cylindrical body formed in longitudinally divided sections, recesses being formed in the opposing faces of said sections to form cavities extending longitudinally thereof; means for securing said sections together; transversely extending shoulders formed upon said sections to restrict the mouths of said cavities; roller cutters; members for carrying said cutters, said members being adapted to repose in said cavities and be movable therein between retracted and extended position relative to said body; lugs provided upon said cutter carrying members to engage said shoulders and retain said members from leaving said cavities; and means for yieldingly urging said cutter carrying members longitu inally in said cavities, cooperating cam surfaces being provided u on said body and said cutter carrying members whereby said cutter carrying members are moved from retracted to extended position in said cavities when responding to said urging means.

5. In an underreamer, the combination of: a cylindrical body formed in longitudinally divided sections, recesses being formed in the opposing faces of said sections to form cavities; means for securing said sections together; shoulders formed upon said sections to restrict the mouths of said cavities; roller cutters; members for carrying said cutters said members being adapted to repose in said cavities and be movable therein between retracted and extended positions relative to said body; lugs provided upon said cuttercarrying members to engage said shoulders and retain said members from leaving said cavities; and means for yieldingly urging said cutter carrying members longitudinally at a uniform rate in said cavities, cooperating cam surfaces being provided upon said body and said cutter carrying members whereby said cutter carryin members are moved from retracted to exten ed position in said cavities when responding to said urging means, the lower portions of said cutter carrying mem bers approaching extended position at a faster rate than the upper portions thereof.

6. An underreamer comprising a body member, upper and lower cutters, means for shiftably mounting said cutters upon said body member so that each has extended and retracted positions relative to said body member, and means for yieldingly urging said cutters from retracted position to extended position, and means causing the lower cutters to reach extended position sooner than the upper cutters when moved under the influence of said urging means.

7. In an underreamer, the combination of: a body member; cutting elements; means for shiftably mounting said cutting elements upon said body member so that each has ex tended and retracted positions relative to said body member; means for yieldingly urging said cutting elements from retracted position to extended position, said last mentioned means causing the lower portions of said cut-v ting elements to approach extended position at a faster rate than the upper portions thereof during the intermediate portion of the movement of the cutting elements.

8. In an underreamer, the combination of an elongated body member, a cavity being formed in and extending longitudinally of the body member, said cavity opening transversely to the outer face of the body member, a cutter element in said cavity and movable longitudinally and transversely therein between retracted'and extended positions relative to said body, means limiting the extent of outward transverse movement of the element, means for urging said element longitudinally through said cavity in one direction, and cam surfaces on said body within the cavity and on the element cooperating to move said element from retracted to extended position when said ele ent is res onding to said urging means, sai cam sur aces being fashioned to cause the lower portions of said element to approach extended position at a faster rate than the upper portions thereof during a portion, at least of such longitudinal movement.

9. In an underreamer, the combination of an elon ated body member, a cavity being former? in and extending longitudinally of the body member, said cavity opening transversely to the outer face of the body member, a cutter element in said cavity and movable 'longitudinally and transversely therein between retracted and extended sitions relative to said body, means limiting the extent of outward transverse movement of the element, means for urging said element longitudinally throu h said cavity in one direction, and cam sur aces on said body within the cavity and on the element coop: erating to move said element from retracted to extended position when said element is responding to said urging means, said cam surfaces being fashioned to cause the lower portions of said element to reach full extended position before the upper portions thereof during such longitudinal movement.

10. In an underreamer, the combination of an elongated body member, a cavity being formed in and extending longitudinally of the body member, said cavity opening transverse- 1y to the outer face of the body member, a cutter element in said cavity and movable longitudinally and transversely therein between retracted and extended ositions relative to said body, means limiting the extent of outward transverse movement of the ele-- ment, means for urging said element longitudinally through said cavity in one direction, and cam surfaces on said body within and partially defining the cavity and on the element cooperating to move said element from retracted to extended position when. said element is responding to said urging means, said cam surfaces being fashioned to cause the lower portions of said element to approach extended position at a faster rate than the upper portions thereof during a portion, at least, of such longitudinal movement.

11. An underreamer comprising a body member, upper and lower cutters, means for shiftably mounting said cutters upon said body member so that each has extended and retracted positions relative to said body mem ber, and means for yieldingly urging said cutters from retracted position to extended position, and means giving the lower cutters greater effective extensive movement than the upper cutters near the beginning of their movement under the influence of said urging means.

12. In an underreamer, the combination of an elongated body member, a cavity being formed in and extending longitudinally of the body member, said cavity opening transversely to the outer face of the bod member, a cutter element in said cavity an movable longitudinally and transverselythereinbetween retra cted and extended positions relative to said body, means limiting the extent of outward transverse movement of the element, means for urging said element longitudinally through said cavity in one direction, and cam surfaces on said body Within the cavity and on the element cooperating to move said element from retracted to extended position when said element is responding to said urging means, there being a fluid passageway through said underreamer from end to end, of which passageway said cavity is a part, and a portion of said cutter element closing off said passageway only when said element is in retracted position.

13. An expansible underreamer comprising a slotted body, an abutment member therein having a reduced portion intermediate its ends, and cutters, each cutter having lateral projections and a recess on its inner face intermediate its ends, said lateral projections bridging the slots in said body to limit displacement of said cutters, said abutment member constituting an abutment for said cutters to hold the cutters in expanded position and to permit collapsion, said recess bridging the reduced portion of said abutment member when the cutters are in exanded condition, recesses extending inthe V ody longitudinally from one end of the body slots and longitudinally overhung by an outer part of the body, and extensions on the cutters adapted to rest in said body recesses when the cutters are in expanded position.

14. An expansible underreamer comprising the combination of a slotted body, a stationary abutment member having a reduced portion intermediate its ends, cutters loosely mounted in said body and limited thereby against outward displacement through said slots, each cutter having a recess with the lower end tapered and provided with means to limit downward travel, said tapered end assisting in expansion of the cutters, recesses extending in the body longitudinally from one end of the body slots and longitudinally overhung by an outer part of the body, and extensions on the cutters adapted to rest in said body recesses when the cutters are in expanded position.

15. In an underreamer, a body with a slotted wall, a longitudinal abutment member within the body and having relatively large and small parts, the surface of the larger part being spaced from the body wall and su stantially parallel to it, a cutter in thewall slot having a win fitting in the space between the wall and t e large part of the abutment member, means to cause relative longitudinal movement between the cutter and abutment member, a recess extending in the body longitudinally from one end of the body slot and longitudinally overhung by an outer part of the body, and an extension on the cutter adapted to rest in said recess when the cutter is in one longitudinal position.

16. In an underreamer, a body with a longitudinally slotted wall, a stationary longitudinal abutment member within the body and having relatively large and small parts, the surface of the larger part being spaced from the body wall and substantially parallel to it, a cutter movable along and in and out through the wall slot and having a wing fitting in the space between the wall and the large abutment part, means to move the cutter longitudinally, a recess extending in the body longitudinally from one end of the body slot and longitudinally overhung by an outer part of the body, and an extension on the cutter adapted to rest in said recess when the cutter is in one longitudinal position.

17. In an underreamer, the combination of a cutter and a cutter supporting body, both cutter and body having two longitudinally spaced laterally projecting parts with a recess between, the cutter and body being relatively movable longitudinally and the two projecting parts of the cutter engaging the two projecting parts of the body in one relative posltion of the cutter, the body having a longitudinally extending recess near one of its projecting parts, which recess is longitudinally'overhung by an outer part of the body, and an end part of the cutter adapted to enter and be confined in said recess when the cutter is in its said one relative position.

18. In an underreamer, a body having a longitudinally extending cutter receiving slot and a longitudinally extending cutter abutment member at the back of the slot, an elongate cutter element movable longitudinally and transversely in the body slot, the abutment member and the cutter element having two longitudinally spaced sets of coacting diagonal faces which act, on longitudinal movement of the cutter element in one direction to move both ends of the cutter element outwardly to expanded position, the body having a recess extending longitudinally from one end of the slot which recess is overhung by an outer part of the body, an end of the cutter element being adapted to enter and be confined in said recess when the element is in expanded position, and means to move the cutter element longitudinally.

19. In an underreamer, a body having a lon 'tudinally extending cutter receiving slot an a longitudinally extending cutter abutment web integral with the body and forming the back wall of the slot, an elongate cutter element movable longitudinally and transversel y in the body slot, the abutment web and the cutter element havin two longitudinally spaced sets of co-acting iagonal faces which act on the cutter element near each of its ends to move the cutter element outwardly to expanded position upon longitudinal movement of the element in one direction, the body having a recess extending longitudinally from one end of the slot which recess is overhung by an outer part of the body, an end of the cutter element being adapted to enter and be confined in said recess when the element is in expanded position, and means to move the cutter element longitudinally.

20. In an underreamer, a body having a longitudinally extending cutter receiving slot and a longitudinally extending cutter abutment web integral'with the body and forming the back wall of the slot, an elongate cutter element movable longitudinally and transversely in the body slot, the abutment web and the cutter element having two longitudinally spaced sets of co-acting diagonal faces which act on the cutter element near each of its ends to move the cutter element outwardly to expanded position upon longitudinal movement of the element in one direction, the body having a recess extendinlongitudinally from one end of the slot whic. recess is overhun by an outer part of the body, one of the iagonal faces on the body making an obtuse angle with the longitudinal and leading substantially directly into the mouth of the body recess, an end of the cutter element being adapted to enter and be confined in said recess when the element is in expanded position, and means to move the cutter element longitudinally.

21. In an underreamer, a body having a longitudinally extending cutter receiving slot and a longitudinall extending cutter abutment member at the back of the slot, an elongate cutter element movable longitudinally and transversely in the body slot, the body having a cutter receiving recess extending longitudinally from one end of the body slot and overhung by an outer part of the body, the inner wall of said recess being substantially parallel with the longitudinal, the abutment member having a diagonal cutter expanding face leading to the mouth of said recess and making an obtuse angle with the longitudinal, the cutter element havingan end adapted to ride said cutter expandlng face into said body recess, and means to urge the cutter element longitudinally against said face and into the recess.

22. In an underreamer, a body, a longitudinally extending cutter element mounted in the body for relative longitudinal and transverse expanding movement, means tendin to cause relative longitudinal movement etween the cutter and body in one direction, the cutter element and body having two longitudinally spaced sets of cutter expanding and supporting surfaces, one set including a body face which makes an obtuse angle with the longitudinal and also a face substantially parallel with the longitudinal, and the other set including a body face which makes an acute angle with the longitudinal.

23. In a reamer, a body with longitudinally extending cutter receivin slots having end walls formed by integra parts of the body, the slots being under-cut so as to be wider at their bottoms than at their mouths, an integral cutter abutment web formed as part of the body and extending longitudinally between the slots, cutters in the slots and fitting into said under-cuts, and the body being divided on a longitudinal plane which passes through both slots.

24. In an underreamer, a body having a longitudinal central axis of rotation, a cutter element movable transversely of the body between contracted and expanded positions, said cutter element embodying a cutter carrier and a cutter proper mounted on the carrier and projecting laterally outwardly therefrom, the carrier having an outer part at one side of the cutter proper, which part lies inside a circumference on the axis as a center and passing through the outermost part of the cutter when the carrier and cutter are expanded, and which said part lies not and cutter are contracted.

25. In an underreamer, a body having a longitudinally extending cutter receiving slot opening out at one side of the body, the body having a longitudinally extending cutter abutment member forming the back wall of the slot and having a cutter receiving recess extending longitudinally from one end of the body slot and outwardly overhung by an outer part of the body, the abutment member having an abrupt cutter expanding face making an obtuse angle with the longitudinal and leading to the mouth of said recess, the inner wall of the recess making a substantially lesser angle with the longitudinal thandoes the expanding face, a cutter clement movable both longitudinally and transversely in the body slot and having an end adapted to ride said cutter expanding face into said body recess, means to urge the cutter element longitudinally against said face and into the recess, and a cutter guiding face on the abutment member at the back of the slot to guide the other end of the cutter element.

26. In an underreamer, an elongate body inside such a circumference when the carrier between the slots and forming their back walls, cutter elements in the slots movable both longitudinally and transversely in a direction toward and away from the backs of the slots, the cutter elements being confined laterally by the side walls of the slots, the body having a cutter receiving recess extending longitudinally from one end of each slot and having a back wall which extends longitudinally, the cutter abutment web having near one end cutter expanding faces making an obtuse angle to the longitudinal and leading to the back walls of said cutter receiving recesses, and having near the other end a longitudinally extending cutter guiding face, the cutter elements having ends adapted to ride the expanding faces into the recesses and having bearings on the guiding faces at their other ends, and means urging the cutter elements longitudinally against the expanding face and into said recess.

In testimony whereof, we have hereunto set our hands at Los Angeles, California, this 6th day of April, 1926.

BERNARD H. SCOTT.

SAMUEL E. ROSS.

NEIL J. NORRIS. 

